'Face blindness' clues uncovered with new brain-zapping test

When Dr. Josef Parvizi of Stanford University asked Ron Blackwell to look around his hospital room, everything seemed fine. His vision was normal. The TV looked like the TV and the “get well” balloons looked like balloons. Parvizi looked just like himself.

“Then they said ‘What do you see now?’” Blackwell recalled to NBCNews.com. “And then colors appeared and I thought that was so amazing. I said ‘How did you do that?’ Then he said ‘OK, what now?’ and I didn’t see anything different, and then he said ‘Look at my forehead,’ and his face changed. His eyes dropped, like, two inches, his nose skewed to his left." When Parvizi asked Blackwell to look at a female assistant in the room, the woman's face appeared to lift upward.

As Parvizi and a Stanford colleague, Kalant Grill-Spector, detail in an article published this month in the Journal of Neuroscience, that’s because Parvizi had sent tiny jolts of electricity into a part of Blackwell’s brain called the fusiform gyrus.

Scientists have known for a while now that people, and at least some primates, have an area of the brain that’s responsible for processing faces specifically. We’ve evolved it, Grill-Spector explained in an interview, because we’re social beings. We need to know who our friends and enemies are, who’s a family member, who we can trust.

If the fusiform gyrus, located in the temporal lobe, is injured, people can lose the ability to recognize faces, even of people they’ve known for a long time. This is called prosopagnosia. People can also be born with prosopagnosia. The neurologist and writer Oliver Sacks, for example, has written about his own struggles with the condition.

People with prosopagnosia, which can be mild to severe, can have difficulty maintaining social relationships. For example, Grill-Spector recalled a young female student who has taken part in her lab studies.

The student had a boyfriend. One day the boyfriend stopped by her room, but he’d just come from playing sports, and was wearing clothes she’d never seen. He was also wet. Missing her usual cues, she didn’t recognize him, and he realized it. That was OK, but his girlfriend thought this stranger was pretty cute and began flirting.

Blackwell doesn’t have prosopagnosia; the experiment was a bit of serendipity. The 47-year-old applications engineer for an electronics company has suffered from epilepsy since childhood. When his seizures became worse in 2010, he consulted with Parvizi.

They decided brain surgery might help. First, though, doctors had to locate the precise origin of the seizures. To do that, they implanted electrodes through Blackwell’s skull and into his brain, including the fusiform gyrus. The idea was to use the electrodes to map the location.

The diagnostic worked, but the surgery couldn’t be done because the originating area was too close to vital tissue.

But Parvizi and Grill-Spector, knowing electrodes were located in and near the fusiform gyrus, wondered if, before they were removed, the devices could be used to map the nerve bundles responsible for face recognition.

“We need a better understanding of the neural basis of prosopagnosia,” Grill-Spector said. “If we can understand the circuit, maybe there’ll be some way in the future to stimulate them in a positive way.”

Blackwell wasn’t told what the experiment was for, so there’d be no risk he’d be “coached” into seeing facial changes. “I figured it was just more testing,” related to the epilepsy, Blackwell said.

After a series of trials, including sham stimulations that produced no effects, and stimulations of two nearby electrodes that did not cause the same kind of facial distortion effects, Parvizi and Grill-Spector concluded they’d located two critical areas in the mid and posterior fusiform gyrus responsible for accurate face viewing. They dubbed them “mFus- and pFus-faces.”

In the end, things worked out for Blackwell, too. He’s on a new drug regimen that has controlled his seizures and, he says, he’s doing “perfectly fine.”

Correction: An earlier version of this story indicated Dr. Kalanit Grill-Spector was in the room at the time of the procedure. She was not.